PROJECT SUMMARY: Cerebral microinfarcts are in association with neurologic dysfunctions in aged and injured brain where they are found to be prevalent, but often escape clinical detection owing to their small sizes. Although evidence suggests that microinfarcts likely have a distinct time course and spatial pattern compared to larger infarcts, spatially-resolved, longitudinal tracking of both hemodynamic and neural responses in the same brain has not been realized, largely due to a lack of methods capable of quantifying multiple neurophysiological and hemodynamic parameters with sufficient spatial resolution over periods of weeks to months. As a result, the neurophysiological consequences of individual or cumulative microinfarcts, including their spatiotemporal evolution and long-term outcome, remain largely unknown, limiting our ability to identify and target them for intervention strategies. The long-term goal is to understand the pathological impacts of microinfarcts with variability, abundance, spatial distribution, occurrence time and risk factors similar to human patients. The objective of this project is to determine the neural and hemodynamic impact of individual and cumulative cerebral microinfarcts in an aged mouse model. The hypothesis is that microinfarcts lead to spatiotemporally varying neuronal impairment and hemodynamic deficits that extend well beyond the lesion site and into chronic time scales, which requires spatially resolving and longitudinal tracking of multiple neurophysiological parameters over weeks to months to reveal their full impacts. We will use two types of ultra-flexible neural electrode arrays for spatially-resolved surface and intracortical recording, both of which are compatible with chronic optical methods. We will combine neural recording with a set of optical systems that are able to induce targeted micro-occlusions with controlled size, location and onset time, and to map and quantify cerebral blood flow and oxygenation over a global field of view and at depth-resolved microscopic scales. Using awake, behaving animals, we will determine 1) the correlation between hemodynamic and neural changes induced by individual microinfarcts, 2) the hemodynamic, neural and behavioral impacts of individual microinfarcts at controlled lesion sizes, and 3) the impacts of cumulative microinfarcts with delayed onset time. The application is highly innovative, in the applicant?s opinion, because it integrates technical advancements on both functional imaging and neural recording to provide a highly novel and powerful combination that permits longitudinal, spatially resolved quantification of multiple neurophysiological parameters in the same brain region and allows for investigation of microinfarcts in previously unattainable regimes. The project will improve the understanding of the physiological impact of microinfarcts and their contribution to neurologic dysfunctions in a variety of neurodegenerative and cerebrovascular diseases that they coexist with, and provide new insight into the therapeutic time window for intervention.